It's called VMT, and it may be what pays to fill potholes and build roads across Idaho in the future. VMT is an acronym for Vehicle Miles Traveled - a distance-based user fee that's being floated in the transportation industry as an alternative to the gasoline tax.

And it's certain to get serious discussion by Gov. C.L. "Butch" Otter's task force, which is doing a top-to-bottom review of highway funding due late next year.

That's because the fuel tax, the mainstay of highway funding across America for 60 years, is dwindling.

"Gas tax probably isn't the long-term solution," Sen. Jim Hammond, R-Post Falls, recently told the Spokane, Wash., Spokesman-Review. Hammond, vice chairman of the Transportation Committee, noted that Idaho gas tax revenues have long been flat and will start to decline as more motorists drive fuel-efficient rigs.

Otter's failed efforts to raise the fuel tax the past two years were at the center of his tempestuous relationship with the Legislature. The governor this year called on lawmakers to gradually raise gas taxes and vehicle registration fees and make other changes to raise a total of $174.5 million more annually for roads after five years. He settled instead for a plan to collect about $54 million a year more for roads after two years. That's now down to $28.4 million.

According to the American Association of State Highway and Transportation officials, the purchasing power of gas taxes nationwide has declined 80 percent since 1993.

In Idaho, fuel tax and vehicle registration revenue - $177.2 million - is down from $177.7 million in 2001.

That's also the trend with other highway funding sources in a soft economy.

Higher fees for drivers licenses and vehicle titles are now expected to bring in $11.5 million, instead of $13.1 million, as recession-weary Idahoans opt to renew their licenses and registrations for shorter periods. Repeal of the ethanol exemption is raising $15.4 million, about $1 million less than anticipated. And legislation estimated to raise $5 million a year from new truck-trailer plates is now expected to bring in just $500,000.

So the name of the game will soon be user fees - maybe eventually including tolls on some of Idaho's busiest highways.

But a mileage tax is likely to get the most traction. Some legislators and even the governor have spoken favorably of the idea in the past.

Simply put, if you drive 15,000 miles a year you'll pay more than if you drive 10,000. The collection mechanism is uncertain - perhaps when you renew your vehicle registration - but for a self-described "user-fee guy" such as Otter, it makes perfect sense.

Long-distance commuters - and as Idaho grows, there will be many more - may not think so, especially in the Treasure Valley where thousands of folks commute from Canyon County to Boise because they can't afford housing in the capital city.

And VMT would hit hard in places like Lincoln County, where 58 percent of the jobs are directly tied to tourism in the Wood River Valley.

But the truth is that states are running out of options.

Across America, there will be 2.9 trillion vehicle miles traveled this year. If motorists were charged a penny a mile, that would go a long way toward fixing the country's crumbling infrastructure.